ALLEN PARK — Cornerback Drayton Florence is the most recent Detroit Lions player to be diagnosed with a concussion.

After the Lions first play on defense on Sunday, Florence had trouble getting back on his feet. He went to the sidelines immediately.

“The official removed him from the game, our guys checked him, he passed all the tests on the sideline,’’ coach Jim Schwartz said Monday. “He returned to play, he played pretty well, he didn’t have any signs as we went forward. He wasn’t having any symptoms after the game.

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“This morning he woke up with a headache — and can’t say mild or severe or anything else,’’ Schwartz added.

According to LiveStrong.com, concussion symptoms can appear immediately after impact or even the next day.

Lions running back Jahvid Best and safety Amari Spievey have been shut down for the season with concussions.

Backus doubtful

Jeff Backus’ streak of starting 186 straight regular season games looks like it could be broken on Thursday.

Backus left Sunday’s game early with a hamstring injury.

“It’s going to be, we’ll see how he does but it’ll be doubtful that he’ll play,’’ Schwartz said on Monday.

“The last time I saw him walk off the field he had a torn bicep, the guy is playing through a lot, he’s a great teammate,’’’ quarterback Matthew Stafford said. “A guy I have a ton of respect for and obviously has blocked for me for the first four years of my career.’’

Backus has started every game since he was drafted in 2001 in the first round. Backus currently holds the mark for the most consecutive starts among active (offensive and defensive) linemen, and he is currently third among all active players with 186 straight starts.

Rookie Riley Reiff finished the game at left tackle and will practice there this week.

Delmas to return?

Safety Louis Delmas has missed three straight games with a lingering knee injury.

He appears to be improving, but he was listed on Monday’s injury report that he would have not practiced. The Lions had to project for the report since they just had a walk-through in preparation for Thursday’s game.

Schwartz said he would “wait and see” about Delmas playing on Thursday.

Ins and outs

If the Lions would have had a full practice on Monday, defensive end Cliff Avril (back), Backus (hamstring), Delmas (knee), Florence (concussion), defensive tackle Sammie Lee Hill (knee), wide receiver Calvin Johnson (knee, thumb) and cornerback Jacob Lacey (foot) would not have practiced.